Question

Neela saves in a ‘Mahila Bachat Gat’ Rs 5 on the first day, Rs 7 on the second day,
Rs 9 on the third day and so on. What will be her savings in the month of August?​

Answer 1

Her savings in the month of August will be ₹1085

Explanation:

GIVEN

a = t1 = 5 , t2 = 7 , t3 = 9

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TO FIND

Her savings in the month of August

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We know that,

August has 31 days

so

We have to find s31

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We know that,

Common Difference ( d ) = t2 - t1

Common Difference ( d ) = 7 - 5

Common Difference ( d ) = 2

Common Difference ( d ) = 2

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We know that,

sn = n / 2 × [ 2a + ( n - 1 ) × d ]

s31 = 31 / 2 × [ 2 × 5 + ( 31 - 1 ) × 2 ]

s31 = 31 / 2 × [ 10 + 30 × 2 ]

s31 = 31 / 2 × [ 10 + 60 ]

s31 = 31 / 2 × 70

s31 = 15.5 × 70

s31 = 1085

s31 = 1085

Her savings in the month of August will be ₹1085

Answer 2

Question

Neela saves in a ‘Mahila Bachat Gat’ Rs 5 on the first day, Rs 7 on the second day, Rs 9 on the third day and so on. What will be her savings in the month of August?

Solution

A.P= 5,7,9,.......

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first term= a = 5

common difference= d = 2

n = no. of days in August month = 31

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Therefore,

Her savings in the month of August=

$= \frac{n}{2}(2a + (n - 1)d) \\ = \frac{31}{2} (2(5) + (31 - 1)2) \\ = \frac{31}{2} (10 + 30 \times 2) \\ = \frac{31}{2} (70) \\ = 31 \times 35 \\ = 1085$

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Her saving in the month of August is Rs 1085.